2 x 6870 temperature difference +/- 14 °C.

[R04dRunn3r]

I have 2 HD6870 in my workstation and use them for Bitcoin mining, but there is huge temperature difference between both cards.

The primaire card runs @ 850 Mhz core, 1050 Mem, Fan 60% 1.137 vcore and the temp is around 80 °C
The secundaire card runs @ 950 Mhz core, 1050 Mem, Fan 60% 1.137 vcore and the temp is around 68 °C

My monitor is connected to the primaire.

Can anybody tell me what the issue is with that, I switched the cards and it doesn't matter, the card in PCIe x16 slot 1 gets hotter than the card in PCIe x16 slot 2.
How is that possible? I have CrossfireX birdge installed but CrossfireX is not enabled in Windows 7.
I have a Gigabyte X58A-OC mb with XFX HD6870 dualfan cards.
Is there something i'm doing wrong or is this normal?

I also have 2 HD5870 running in another system and there temp diff is only +/- 3 °C
That system has the monitor connected to the secundaire card and that one runs hotter than the primaire card.

Correct me if I'm wrong but whatever card I connect the monitor to gets hotter than the one without a monitor, or is this just BS?

[aurigus]

Could be due to the proximity to the CPU or another architectural reason. Since it is always in that slot, likely it is something with the motherboard causing this and not a difference between the cards.

[abeaulieu]

Can anybody tell me what the issue is with that, I switched the cards and it doesn't matter, the card in PCIe x16 slot 1 gets hotter than the card in PCIe x16 slot 2.
How is that possible? I have CrossfireX birdge installed but CrossfireX is not enabled in Windows 7.
I have a Gigabyte X58A-OC mb with XFX HD6870 dualfan cards.
Is there something i'm doing wrong or is this normal?

It seems like the most likely cause of this temperature difference is the location of the slot. I am assuming that since you seem to be using this mining computer as a desktop, it is in an vertical case (typical). You are saying that PCIe x16 slot #1 is hotter, which is most likely above PCIe #2 on the motherboard which makes it vertically above PCIe slot #2 (correct?).

Now in terms of airflow: The bottom video card would be taking the cooler air that is likely at the bottom of the case, drawing it in through the fan(s), and then spitting it back out between the fins of the heat sink. The top video card will take in the air that is directly beneath the fan(s) and doing the same thing. However, much of this air that the top card takes in has already been heated by the bottom card.

This is my guess, and I believe that it is quite common. I would look into directly controlling the fan speeds (fan speed of the top card would be significantly higher). Or you can switch to a typical mining rig setup where you lay the mining rig down without a case (mobo is parallel to the ground). This allows some hot air to exit upwards without the case stopping it (note that the "top" card will still run a little hotter).

Hope this helps.

[abeaulieu]

A good test to see what is actually going on in your system would be to run the cards separately. In other words, remove the bottom card run the top card and see how hot it gets. Then remove the top card, place the bottom card in the top slot, and see how hot it gets.

If you control this test properly you should be able to see what is normal for each card without experiencing effects from the other card (use the same slot because there might be a temperature difference or difference in air flow from one slot to another).

[R04dRunn3r]

I have a photo that gives a good look of the setup.
But do you all have comparable temp diff, when running 2 or more videocards?
I'm thinking about buying a third videocard, have one PCIe x8 slot empty and the PSU can handle it (I think  ) but I have nog idea wich one, am looking for a cheap 5970 to place between the 6870's but again I think that the temps will go to the roof without some extreme cooling or having a workstation that sounds like a small vacuum cleaner.
It's already a small dustbucket!
http://edental.home.xs4all.nl/bitcoin/Rig1a.jpg

[Miner612]

Your primary GPU will always run hotter.  Monitor plugged in or not.  It is my understanding that the motherboard treats slot 0 different than others.

[abeaulieu]

What is it the bottom right of your case (at the front)? Harddrive(s)?

You might want to consider moving them up in the case (I doubt they really need much cooling) like where your CD drive bays are. Then you can put in a decent fan there if there isn't already one. I like to control airflow through my case when I have it closed. That fan would create a fresh air intake in the front there and blow directly onto your video cards.

Also you might want to consider how your cable management is affecting airflow.

[RandyFolds]

Do you run with an open case? They are designed for flow-through, and popping off the cover tends to just make them spin their wheels in place, so to speak. None of the heated air is being blown away from the source, merely blown around it without any real venting. My boxes run cooler when closed and with properly oriented fans, meaning all the same direction...some drawing air in, others forcing it out, but all in line with one another.